What an absurd double standard. The language is patterned after GitHub's own caveats about misuse of GitHub Pages:
> you may receive a polite email from GitHub Support suggesting strategies[… such as, and including] moving to a different hosting service that might better fit your needs
GitHub Pages has never been a free-for-all. The acceptable use policy makes it clear:
> the primary focus of the Content posted in or through your Account to the Service should not be advertising or promotional[…] You may include static images, links, and promotional text in the README documents or project description sections associated with your Account, but they must be related to the project you are hosting on GitHub